From Ukrainian Heraldry site:
"It is known since X century under the name
"Muncash" (from Hungarian word meaning "a
worker") as a settlement in a Carpathian lowland. The first
written documents were found in chronicle "Gesta
Hungarorum" in XII century. In 1376 it was given a right to
have a seal with a picture of St.Martin, a bishop and patron of a
local church."Dov Gutterman, 21 October 2000

Mukachevo readopted its original Coat of Arms. The city hasn't
got flag yet.Source: Mihály Szemák from MukachevoIstván Molnér, 20 May 2001